Pancreatin is a mixture of several digestive enzymes produced by the exocrine cells of the pancreas. It is composed of amylase, lipase and protease. The pancreas gland produces both endocrine secretions that enter the blood stream and exocrine secretions that enter the duodenum. Whereas the endocrine secretions comprise hormones such as insulin and glucagon, the exocrine secretions to a large part are made up of enzymes necessary for digestion of food in the duodenum.
In particular, pancreatic lipase contains a polypeptide co-factor named colipase. Pancreatic lipase is inactivated by bile salts in the concentrations they occur in the small intestine. The function of colipase is to reactivate bile salt-inhibited lipase. The function of lipase in the intestine depends on the presence of an adequate concentration of colipase. A colipase deficiency could lead to poor digestion and mal-absorption of fat. Colipase has two important surfaces, a hydrophilic surface that interacts with lipase and a hydrophobic surface that presumably interacts with substrate (fat). Hermoso (1996) reported the X-ray structure of the porcine pancreatic lipase (PL)-colipase (CL) complex obtained in the presence of the C8E4 non-ionic detergent (Hermoso, J. et al., The Journal of Biological Chemistry, 271, 18007-18016 (1996)).
Colipase has no lipolytic activity of its own, but the lipase activity is proportional to the amount of colipase present (“colipase activity”) under physiological conditions, i.e. colipase binds to lipase in a 1:1 molar ratio. Therefore, colipase activity can be defined in operational terms as the capacity to reactivate pure pancreatin lipase in the presence of supramicellar concentrations of bile salt (Gaskin, K. J. et. al., The Journal of Clinical Investigation, 69(2): 427-434 (1982)).
The current USP monograph is silent as to colipase and how to test its level in, for example, a pancreatin active pharmaceutical ingredient (API). It is therefore desirable to develop an assay method to measure the amount of colipase present in a pancreatin sample and to verify saturation levels that are present in pancreatin API.